Step-by-Step Instructions
Preheat oven: Set to 375°F (190°C). Line a muffin tin with paper liners.
Mix dry ingredients: In a bowl, whisk flour, baking powder, baking soda, salt, and cinnamon.
Prepare wet ingredients: In another bowl, whisk eggs, sugars, oil, milk, and vanilla until smooth.
Combine: Gradually fold dry ingredients into wet. Stir until just combined — don’t overmix.
Add apples: Gently fold in diced apples.
Fill muffin tin: Divide batter evenly into liners, filling about ¾ full.
Make streusel: In a small bowl, mix flour, brown sugar, and cinnamon. Cut in cold butter with a fork until crumbly. Sprinkle over each muffin.
Bake: 20–25 minutes, or until golden brown and a toothpick comes out clean.
Cool: Let muffins rest in the tin for 5 minutes, then transfer to a wire rack.